From Glitch City Laboratories

Luck manipulation or RNG abuse (pseudorandom number generator abuse in full), or RNG manipulation refers to making a future event that is supposed to be random predictable, such as whether a wild Pokémon is shiny or has good IVs, or achieving a desired 'random' outcome through trial and error by frame-by-frame advance and save states.

Like how the result of rolling a dice depends on factors like the angle of the throw, computers and video games are not truly random, as the result must be calculated from something that is not random to begin with, though highly unpredictable values may be used in the process of making something seem random.

If the game follows exactly the same inputs, and if the conditions prior to starting the game remain the same, then results will be the same, regardless of measures to make something 'random'.

This is why tool assisted speedruns (TASes) can be played back on an emulator/console (through the use of a machine) without the need of encoding them as a video, but de-synchronization may occur if a different emulator/console than the original is used to play the recording.